The present invention relates to a zoom lens system having high zoom ratio.
Japanese Laid-Open Patent Publication No. H04-78809 discloses a camera zoom lens that has five lens groups and a high zoom ratio of around six. In order from the object side to the image forming side, this zoom lens includes four groups with positive, negative, positive, and positive refractive powers, and a fifth lens group with a comparatively low refractive power. During zooming, the first, third and fifth groups are fixed, the second group moves in a certain direction to change the magnification, and the fourth group is moved forward and backward to correct variation in the image plane during zooming. In addition, focusing is carried out by moving the fourth group.